Method for controlling carbon content in nickel-based superalloy powder produced from coarse powder return

Abstract

This invention discloses a method for controlling the carbon content of nickel-based superalloy powder prepared from recycled coarse powder. The method involves detecting the carbon and oxygen content of the recycled coarse powder and the master alloy rod before smelting, and calculating the average carbon and oxygen content based on the charging ratio. The carbon loss in the melt is determined by considering the carbon-oxygen reaction mechanism under smelting conditions. The required theoretical carbon replenishment is calculated based on a set target carbon content, and a stepped carbon replenishment scheme is determined according to the carbon content level of the master alloy rod. The carbon replenishment material is mechanically crushed graphite electrode fragments wrapped in nickel foil, which are added to a crucible along with the recycled coarse powder and the master alloy rod. Vacuum induction melting is performed under vacuum conditions of 1.0 Pa to 2.0 Pa and a temperature of 1500℃ to 1600℃, followed by powder preparation via gas atomization. After powder preparation, the carbon content of the powder is detected, and the carbon replenishment scheme for subsequent furnace batches is adjusted based on the results, thereby achieving closed-loop control. This invention can solve the problem of difficult-to-control carbon content fluctuations in the powdering process of coarse powder return material, realize the stable and precise control of carbon content in nickel-based high-temperature alloy powder, effectively improve the compositional stability between powder batches, and is suitable for vacuum induction melting gas atomization (VIGA) powdering process containing coarse powder return material.

Description

Technical Field

[0001] This invention relates to the fields of powder metallurgy and high-temperature alloy powder production technology, and in particular to a method for stable control of carbon content in nickel-based high-temperature alloy powder by detecting the carbon and oxygen content of the raw materials, calculating carbon loss, and supplementing carbon using graphite electrode fragments wrapped in nickel foil under the condition of using coarse powder return material. Background Technology

[0002] High-temperature alloy powder is a key raw material for core hot-end components such as powder turbine disks, and is usually prepared using argon atomization powder preparation technology. During the powder and disk preparation process, a large amount of coarse powder is generated. Due to requirements such as inclusion size control, coarse powder cannot be directly used in the manufacture of powder turbine disks. Therefore, in industrial production, coarse powder is recycled as smelting raw material to improve raw material utilization and reduce costs.

[0003] When coarse powder is added and the number of times it is returned increases during the remelting and powdering process, trace elements such as carbon are easily burned off, which can easily cause the chemical composition of the powder to deviate from the design value or even exceed the standard requirements, making it difficult to meet the batch stability requirements of the powder turbine disk for the powder composition.

[0004] Existing technologies do not disclose a method for dynamically calculating carbon loss based on oxygen content, nor do they combine step-by-step carbon replenishment with powder detection to form a closed-loop control. Therefore, there is a lack of precise control methods for the carbon content of atomized nickel-based superalloy powder from coarse powder return materials. Thus, there is an urgent need to propose a new technical solution to achieve precise control of powder carbon content through step-by-step carbon replenishment, ensuring batch-to-batch stability of powder composition. Summary of the Invention

[0005] The purpose of this invention is:

[0006] This invention addresses the problems of large fluctuations and difficulty in controlling the carbon content of nickel-based superalloy powder during the powdering process of recycled coarse powder. To this end, a control method is proposed, the implementation of which is as follows: Before melting, the carbon and oxygen contents of the recycled coarse powder and the master alloy rod are detected, and the average carbon and oxygen contents of the raw materials are calculated; then, combined with a carbon loss calculation model, the theoretical carbon replenishment amount is obtained; subsequently, based on the carbon content level of the master alloy rod, a stepped carbon replenishment scheme is determined, and graphite electrode fragments wrapped in nickel foil are loaded into a crucible along with the recycled coarse powder and the master alloy rod, and melted under vacuum induction melting conditions, followed by powdering through a gas atomization process; finally, the carbon content of the powder is detected, and the subsequent carbon replenishment scheme is adjusted, thereby achieving stable control of the carbon content.

[0007] The technical solution of this invention is:

[0008] A method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder is provided, including the following steps:

[0009] Step 1: Composition analysis of coarse powder return material and master alloy bar stock:

[0010] Before smelting and grinding, the furnace charging raw materials consist of coarse powder return material and master alloy bar stock. Based on the carbon and oxygen content of the coarse powder return material and the master alloy bar stock, the average carbon content of the furnace charging raw materials is calculated. and average oxygen content The formula is:

[0011]

[0012] in, This refers to the proportion of coarse powder return material in the furnace charge feedstock. This is the proportion coefficient of the master alloy bar in the furnace charge. and The sum is 1. The carbon content of the coarse powder return feed. The oxygen content of the coarse powder return feed. The carbon content of the master alloy bar. Oxygen content of the master alloy bar;

[0013] Step 2: Calculation of carbon loss and determination of theoretical carbon replenishment:

[0014] Carbon loss due to vacuum high-temperature smelting of coarse powder return material Calculate according to the following formula:

[0015]

[0016] in, For carbon monoxide content, The value should be in the range of 0.6 to 0.7, with a preferred value of 0.65. The fraction of reducible oxygen. The selected value is in the range of 0.8 to 0.9, with an optimal value of 0.85. The average oxygen content of the raw materials charged into the furnace;

[0017] With target carbon content Based on the average carbon content and carbon loss of the raw materials charged into the furnace, the theoretical carbon replenishment amount is determined. The formula is:

[0018]

[0019] in, For the target carbon content, The average carbon content of the feedstock. Carbon loss This refers to the total mass of the raw materials charged into the furnace;

[0020] Step 3: Develop a tiered carbon supplementation plan:

[0021] Based on the carbon content level of the master alloy bar, a scheme for determining the furnace charging quality of graphite electrode materials for smelting is formulated:

[0022]

[0023] Step 4, Melting and Atomization Powdering:

[0024] The quality of the graphite electrode material is determined according to step 3. The graphite electrode material wrapped in nickel foil is then loaded into the crucible along with the furnace raw material as the smelting raw material. Vacuum induction melting is carried out under smelting process conditions of vacuum degree 1.0 Pa~2.0 Pa and temperature 1500℃~1600℃ to fully melt and homogenize the smelting raw material. Subsequently, nickel-based high-temperature alloy powder is prepared by gas atomization process.

[0025] Step 5: Powder carbon content detection and model optimization:

[0026] After the powder preparation is completed, the carbon content of the powder is tested, and the measured results are used to optimize subsequent furnace batches.

[0027] Furthermore, the average carbon content and oxygen content of the furnace charge are calculated using a weighted method based on the weight ratio of the raw materials, and the average value of the detected values ​​of the coarse powder return material and the master alloy bar material is calculated based on their weight ratio.

[0028] Furthermore, the carbon loss during the smelting process is corrected for changes in vacuum level and smelting temperature during calculation to ensure that the calculation is closer to reality.

[0029] Furthermore, the coarse powder return material is subjected to low-temperature vacuum drying before being added to remove adsorbed moisture and reduce the oxygen content entering the melt.

[0030] Furthermore, the mass percentage of coarse powder return material in the furnace feed should be controlled between 20% and 50%. A lower percentage is not conducive to improving the utilization rate of raw materials, while a higher percentage can easily lead to increased oxygen content and fluctuations in carbon loss.

[0031] Furthermore, the graphite electrode fragments are evenly distributed during furnace loading to facilitate the uniform dissolution of carbon in the alloy after melting.

[0032] Furthermore, in step 4, the raw materials for loading the furnace and the graphite electrode material wrapped in nickel foil are loaded into the crucible in batches. The order of each batch is as follows: first, the master alloy rod is added, then the coarse powder return material is placed, and finally the graphite electrode material wrapped in nickel foil is added. Each batch is cycled in this order until the loading of the furnace is completed.

[0033] Furthermore, in step 4, the melted and homogenized melt is kept at a temperature for 5 to 10 minutes before atomization, and electromagnetic stirring is performed during the holding process to ensure a more uniform carbon distribution.

[0034] Furthermore, when optimizing subsequent furnace runs, the difference between the test results of the previous few furnace runs and the target carbon content is referenced, and the amount of carbon supplementation for the next furnace run is adjusted accordingly.

[0035] The advantages of this invention are:

[0036] Compared with existing technologies, the method of this invention, by detecting the carbon and oxygen content of the coarse powder return material and the master alloy bar stock, and combining it with the carbon loss calculation formula, can quantitatively assess the carbon consumption during the smelting process, avoiding the uncertainty caused by purely empirical judgment. It combines theoretical calculation with a step-by-step carbon replenishment scheme, unifying accuracy and operability. Using graphite electrode fragments wrapped in nickel foil as the carbon replenishment material ensures a clean and controllable carbon replenishment process, avoiding the problems of impurities and uneven dispersion easily introduced by powder feeding. The carbon content of the powder obtained by the above method is close to the target value, improving the consistency and stability of the nickel-based superalloy powder composition. Compared with traditional methods, the fluctuation range is reduced from 0.0075% to 0.001%. The step-by-step carbon replenishment scheme of this invention is applicable when the carbon content of the master alloy is between 0.045% and 0.060%. Detailed Implementation

[0037] A method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder is provided, including the following steps:

[0038] Step 1: Composition analysis of coarse powder return material and master alloy bar stock:

[0039] Before smelting and grinding, the furnace charging raw materials consist of coarse powder return material and master alloy bar stock. Based on the carbon and oxygen content of the coarse powder return material and the master alloy bar stock, the average carbon content of the furnace charging raw materials is calculated. and average oxygen content The formula is:

[0040]

[0041] in, This refers to the proportion of coarse powder return material in the furnace charge feedstock. This is the proportion coefficient of the master alloy bar in the furnace charge. and The sum is 1. The carbon content of the coarse powder return feed. The oxygen content of the coarse powder return feed. The carbon content of the master alloy bar. Oxygen content of the master alloy bar;

[0042] Step 2: Calculation of carbon loss and determination of theoretical carbon replenishment:

[0043] Carbon loss due to vacuum high-temperature smelting of coarse powder return material Calculate according to the following formula:

[0044]

[0045] in, For carbon monoxide content, The value should be in the range of 0.6 to 0.7, with a preferred value of 0.65. The fraction of reducible oxygen. The selected value is in the range of 0.8 to 0.9, with an optimal value of 0.85. The average oxygen content of the raw materials charged into the furnace;

[0046] With target carbon content Based on the average carbon content and carbon loss of the raw materials charged into the furnace, the theoretical carbon replenishment amount is determined. The formula is:

[0047]

[0048] in, For the target carbon content, The average carbon content of the feedstock. Carbon loss This refers to the total mass of the raw materials charged into the furnace;

[0049] Step 3: Develop a tiered carbon supplementation plan:

[0050] Based on the carbon content level of the master alloy bar, a scheme for determining the furnace charging quality of graphite electrode materials for smelting is formulated:

[0051]

[0052] Step 4, Melting and Atomization Powdering:

[0053] The quality of the graphite electrode material is determined according to step 3. The graphite electrode material wrapped in nickel foil is then loaded into the crucible along with the furnace raw material as the smelting raw material. Vacuum induction melting is carried out under smelting process conditions of vacuum degree 1.0 Pa~2.0 Pa and temperature 1500℃~1600℃ to fully melt and homogenize the smelting raw material. Subsequently, nickel-based high-temperature alloy powder is prepared by gas atomization process.

[0054] Step 5: Powder carbon content detection and model optimization:

[0055] After the powder preparation is completed, the carbon content of the powder is tested, and the measured results are used to optimize subsequent furnace batches.

[0056] Before being added, the coarse powder return material is dried under low temperature and vacuum to remove adsorbed moisture and reduce the oxygen content entering the melt.

[0057] The mass percentage of coarse powder return material in the furnace feed should be controlled between 20% and 50%. A lower percentage is not conducive to improving the utilization rate of raw materials, while a higher percentage can easily lead to increased oxygen content and fluctuations in carbon loss.

[0058] The graphite electrode fragments are evenly distributed during furnace loading to facilitate the uniform dissolution of carbon in the alloy after melting.

[0059] In step 4, the raw materials for loading the furnace and the graphite electrode material wrapped in nickel foil are loaded into the crucible in batches. The order of each batch is as follows: first, add the master alloy rod, then add the coarse powder return material, and finally add the graphite electrode material wrapped in nickel foil. Each batch is cycled in this order until the loading of the furnace is completed.

[0060] In step 4, the melted and homogenized melt is kept at a temperature for 5 to 10 minutes before atomization, and electromagnetic stirring is performed during the holding process to ensure a more uniform carbon distribution.

[0061] Descriptions of various advantageous arrangements have been shown for illustrative and descriptive purposes, but such descriptions are not intended to be exclusive or limited to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. Furthermore, different advantageous examples may describe different advantages compared to other advantageous examples. One or more examples have been selected and described in order to best illustrate the principles and practical application of the examples, and to enable those skilled in the art to understand that this disclosure contains various examples with various modifications suitable for the particular intended use.

Claims

1. A method for controlling the carbon content of a nickel-based superalloy powder produced from a coarse powder return, characterized in that, Includes the following steps: Step 1: Composition analysis of coarse powder return material and master alloy bar stock: Before smelting and powdering, the charging raw material composed of the coarse powder return material and the master alloy bar material is obtained, and the average carbon content and the average oxygen content of the charging raw material are calculated according to the carbon content and the oxygen content of the coarse powder return material and the carbon content and the oxygen content of the master alloy bar material and the average oxygen content , and the formula is: wherein is a proportionality coefficient for the proportion of the coarse powder return in the charge material, is a proportionality coefficient for the proportion of the master alloy rod in the charge material, and sum up to 1, is the carbon content of the coarse powder return, is the oxygen content of the coarse powder return, is the carbon content of the master alloy rod, is the oxygen content of the master alloy rod; Step 2: Calculation of carbon loss and determination of theoretical carbon replenishment: Carbon loss due to coarse powder return material under vacuum high temperature melting conditions was calculated according to the following formula: in, For carbon monoxide content, The value ranges from 0.6 to 0.

7. The fraction of reducible oxygen. The selected value should be in the range of 0.8 to 0.

9. The average oxygen content of the raw materials charged into the furnace; With target carbon content Based on the average carbon content and carbon loss of the raw materials charged into the furnace, the theoretical carbon replenishment amount is determined. The formula is: in, For the target carbon content, The average carbon content of the feedstock. Carbon loss This refers to the total mass of the raw materials charged into the furnace; Step 3: Develop a tiered carbon supplementation plan: Based on the carbon content level of the master alloy bar, a scheme for determining the furnace charging quality of graphite electrode materials for smelting is formulated: Step 4, Melting and Atomization Powdering: The quality of the graphite electrode material is determined according to step 3. The graphite electrode material wrapped in nickel foil is then loaded into the crucible along with the furnace raw material as the smelting raw material. Vacuum induction melting is carried out under smelting process conditions of vacuum degree 1.0 Pa~2.0 Pa and temperature 1500℃~1600℃ to fully melt and homogenize the smelting raw material. Subsequently, nickel-based high-temperature alloy powder is prepared by gas atomization process. Step 5: Powder carbon content detection and model optimization: After the powder preparation is completed, the carbon content of the powder is tested, and the measured results are used to optimize subsequent furnace batches.

2. The method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder as described in claim 1, characterized in that: The average carbon and oxygen content of the furnace charge is calculated using a weighted method based on the weight ratio of the raw materials. The average value of the test values ​​of the coarse powder return material and the master alloy bar material is calculated based on the weight ratio.

3. The method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder as described in claim 1, characterized in that: The carbon loss during the smelting process is corrected for changes in vacuum level and smelting temperature during calculation.

4. The method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder as described in claim 1, characterized in that: Before being added, the coarse powder return material is dried under low temperature and vacuum to remove adsorbed moisture and reduce the oxygen content entering the melt.

5. The method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder as described in claim 1, characterized in that: The mass percentage of coarse powder return material in the furnace charge should be controlled between 20% and 50%.

6. The method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder as described in claim 1, characterized in that: The graphite electrode fragments are evenly distributed during furnace loading.

7. The method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder as described in claim 1, characterized in that: In step 4, the raw materials for loading the furnace and the graphite electrode material wrapped in nickel foil are loaded into the crucible in batches. The order of each batch is as follows: first, add the master alloy rod, then add the coarse powder return material, and finally add the graphite electrode material wrapped in nickel foil. Each batch is cycled in this order until the loading of the furnace is completed.

8. The method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder as described in claim 1, characterized in that: In step 4, the melted and homogenized melt is kept at a temperature for 5 to 10 minutes before atomization, and electromagnetic stirring is performed during the holding process.

9. The method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder as described in claim 1, characterized in that: When optimizing subsequent furnace runs, the difference between the test results of the previous few furnace runs and the target carbon content is referenced, and the amount of carbon supplementation for the next furnace run is adjusted accordingly.

10. The method for controlling the carbon content in nickel-based superalloy powder prepared from recycled coarse powder as described in claim 1, characterized in that: In step 2, The value is 0.

65. The value is 0.85.

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